Conventionally, in an electrophotographic image forming apparatus, depending on an operator (user), a cartridge type in which the cartridge is mounted in and demounted from the apparatus main assembly is employed. According to this cartridge type, maintenance of the electrophotographic image forming apparatus can be performed by the user himself (herself) without relying on a service person, and therefore operativity can be remarkably improved. For this reason, the cartridge type has been widely used in the electrophotographic image forming apparatus.
As a constitution of the cartridge, a constitution in which the cartridge is mounted in and demounted from the apparatus main assembly in a predetermined direction substantially perpendicular to an axis of a rotatable member such as the photosensitive drum has been known. As a constitution of the apparatus main assembly, a constitution in which a main assembly-side engaging portion for transmitting the rotational force to the photosensitive drum is provided and a coupling member provided in the cartridge is engaged with the main assembly-side engaging portion, and thus the rotational force is transmitted from the main assembly-side engaging portion to the cartridge via the coupling member has been known.
In such a cartridge type, a constitution in which the coupling member and a rotational force receiving member (member to which the rotational force is to be transmitted) are provided in a photosensitive drum unit and a part of the coupling member is accommodated in the rotational force receiving member, and the coupling member is tiltable relative to an axis of the photosensitive drum unit is employed. In this constitution, with a mounting and demounting operation of the cartridge relative to the apparatus main assembly, an engaging operation and a demounting operation of the coupling member can be performed. In addition, such a constitution that the coupling member and the rotational force receiving member are connected with each other by a shaft portion and thus the rotational force transmitted from the main assembly-side engaging portion to the coupling member is transmitted from the member to the rotational force receiving member via the shaft portion has been known (Japanese Laid-Open Patent Application (JP-A) 2014-112169).
However, in a conventional constitution disclosed in FIG. 20 of JP-A 2014-112169, in order to transmit the rotational force from the coupling member to the rotational force receiving member, the rotational force receiving member is provided with a groove portion for supporting the shaft portion. Then, the shaft portion contacts the groove portion of the rotational force receiving member, so that the rotational force is transmitted from the coupling member to the rotational force receiving member. In such a case, the rotational force is exerted on the groove portion of the rotational force receiving member, so that depending on a magnitude of the rotational force, not only the groove portion of the rotational force receiving member but also the rotational force receiving member itself largely deform in some instances. As a result, the rotational force receiving member rotates in a distorted state, so that there is a possibility that rotation of the rotational force receiving member and the photosensitive drum unit with high accuracy is impaired.
Further, in the rotational force receiving member, rotates where the groove portion is provided and the groove portion is not provided co-exist, so that a shape of the rotational force receiving member becomes complicated. In such a case, when the rotational force receiving member is molded, flowability of a resin material becomes non-uniform, so that it becomes difficult to mold the rotational force receiving member with high accuracy in some instances.